A number of frame and frameless stereotactic systems have been developed to assist surgeons during various procedures that require an instrument to travel to a target within a body. Typically, a surgeon analyzes images of the body (e.g., CT scans, MRI scans, or PET scans) to determine the location of the target and to determine a desirable trajectory along which the instrument should travel during the surgical procedure.
Frameless stereotactic systems do not require the body to be mechanically fixed directly to a reference frame or other device during the surgical procedure. In addition, frameless stereotactic systems are generally less invasive and allow a surgeon to move a surgical instrument in any desired direction without being restricted by cumbersome mechanical structures. As such, frameless stereotactic systems often reduce the amount of patient trauma associated with certain surgical procedures while providing the surgeon with an adequate amount of positional freedom during surgery.
Conventionally, stereotactic systems attempt to determine the precise location of the surgical instrument relative to a reference point within a coordinate system. Some frameless stereotactic systems utilize sophisticated optical, RF, magnetic, audio, or other methodologies to generate a three dimensional reference volume around the surgical area. Typically, the surgical instrument carries a system-compatible emitter or sensor, and the position of the instrument is determined relative to a number of reference points to facilitate precise location analysis anywhere within the reference volume.
Many surgical procedures require the surgeon to approach a target along a predetermined trajectory. As such, knowledge of the precise location of the surgical instrument within the entire field of operation may not be useful to the surgeon. In other words, the surgeon may primarily need guidance to the predetermined target rather than knowledge of the exact location of the instrument at all times.
Some conventional stereotaxic systems utilize software programs and realtime position feedback techniques to precisely locate the instrument. The data generated by such systems may be difficult to interpret unless the operator is very familiar with the particular system. Thus, surgeons and medical technicians may require extensive training before they can efficiently operate these systems. The complex software and extensive training increases the expense of such systems and results in reluctance by the surgeons to use such systems. Thus, these systems do not get widespread use.
Frameless stereotactic systems may also employ a number of sensitive electronic components. Due to the precision and sensitivity of the electronic components, complex and time consuming calibration and set-up procedures are needed. These procedures may involve the patient prior to commencement of the surgery. This approach may lengthen the amount of time that the patient is under anesthesia thereby increasing the medical risks to the patient.
Other frameless stereotactic systems that precisely locate and orient the instrument may overly restrict the amount of positional freedom available to the surgeon during free-hand surgery. For example, a surgeon may desire to change the trajectory to a target during surgery. A change in the trajectory may be desired to avoid critical or eloquent areas of the brain to the maximum extent possible to prevent permanent brain damage or excessive bleeding. In such a situation, a surgeon may desire to select new surgical entry point. These stereotactic systems may not be able to provide guidance along a new trajectory without extensive, time consuming recalibration and realignment.